Load Sensor Balancer Instruments

ABSTRACT

Disclosed herein are apparatuses and methods for performing joint balancing procedures. The apparatus may have femoral paddle and a tibial paddle attached to a housing. The housing may include a distraction mechanism to vary the space between the femoral paddle and the tibial paddle. The tibial paddle may lie entirely within the femoral paddle in a closed position. A load sensor may be placed in the femoral paddle to measure ligament tension. The apparatus may be inserted into a knee joint and positioned to remain within the knee joint during flexion and extension of the knee without everting a patella.

FIELD OF INVENTION

The present disclosure relates to an apparatus and a method forperforming orthopedic procedures, and in particular to an apparatus anda method for performing joint replacement procedures.

BACKGROUND OF THE INVENTION

Joint replacement procedures generally include replacing a subject'sjoint with prosthetic joint components. For example, a total kneearthroplasty (“TKA”) procedure includes replacement of the distal end ofthe femur and the proximal end of the tibia with a femoral prosthesisand a tibial prosthesis, respectively. Multiple bone resections on thedistal femur and the proximal tibia are required prior to theimplantations of these prostheses. Proper soft-tissue tension, jointalignment and balance are necessary for smooth and well-aligned jointmovement.

Various surgical tools such as tensors, balancer, spacers, alignmentguides, load indicators, etc. are generally used to perform a TKA. Afterthe initial bone resections of the tibia and/or the femur, a surgeondetermines the knee extension and flexion gaps using tools such asspacers, a tensor, or a balancer. Spacers typically consist of a set ofone-piece blocks of varying thicknesses that can be inserted into theresected joint space to confirm the flexion and extension gaps. A tensoror balancer generally have multiple components including a set ofpaddles with telescoping means to allow for insertion into the jointspace and distraction in situ. The tensor must be structurally strongenough to withstand substantial loading during flexion and extension ofthe knee. However, a tensor with large paddles cannot be easily locatedwithin the tight joint space, especially during the initial insertionprior to distracting the knee joint.

Knee joint balancing with the tensioner may be performed during the TKAwithout everting the patella. This generally requires a tensor withsufficiently long linking members and femoral/tibial paddles that areoffset to the linking members for the placement of the tensioner inanterior-to-posterior direction without requiring the dislocation of thepatella from the trochlear groove of the femur. However, long linkingmembers have a tendency to induce cantilever loading and offset paddlescause torsion loading which reduces the load bearing capability of thetensor. Joint balancing may also be performed by everting the patellawhich may allow for the use of a tensioner without the attendantproblems just mentioned. However, dislocating the patella in this mannercan damage the soft tissue of the extensor mechanism. Moreover, acomplete and accurate assessment of the joint's balance through aflexion-extension range of motion cannot be assessed.

Furthermore, load sensors which can be used with the tensors to providereal-time ligament tension during the TKA must be placed in contact withthe paddles. These sensors further increase the size of the tensorpaddles and increase the difficulty of locating the paddles in a tightjoint space.

Therefore, there exists a need for an apparatus and a method that allowfor soft tissue balancing and proper knee alignment during a kneereplacement procedure.

BRIEF SUMMARY OF THE INVENTION

In certain embodiments, the present disclosure relates generally to atensor with a tibial paddle that can lie within a femoral paddle andmethods for performing a joint balancing using the tensor. In otherembodiments, the present disclosure relates generally to a tibial spacerand balancer and methods for performing a joint balancing using thetibial spacer and balancer.

In an aspect of the present disclosure, an apparatus for performing anorthopedic procedure on a knee is provided. In accordance with thisaspect, the apparatus may include a femoral paddle, a tibial paddle, aload sensor and a housing. The femoral paddle may define a thickness.The femoral paddle may have a proximal side and an opposite distal side.The proximal side may include at least one proximal femoral recess. Thedistal side may include a distal femoral recess. The tibial paddle mayinclude a tibial proximal side and an opposite tibial distal side. Theload sensor may be disposed in the femoral recess to indicate a load onthe femoral paddle. The housing may be coupled to the tibial paddle andthe femoral paddle. The housing may include a distractor to vary thedistance between the tibial paddle and the femoral paddle. The tibialpaddle may be disposed within the distal femoral recess in a closedposition such that a combined thickness of the femoral paddle, thetibial paddle and the load sensor in the closed position may besubstantially the same as the thickness.

Continuing in accordance with this aspect, the femoral paddle mayinclude a plurality of tiered recesses within the distal femoral recess.The tibial paddle may include a plurality of tiered ribs on the tibialproximal side. Each of the plurality of tiered ribs may be disposedwithin a corresponding tiered recess in the closed position. At leastone of the tiered ribs may contact a distal surface of the correspondingtiered recess in the closed position.

Continuing in accordance with this aspect, the femoral paddle may extendalong a central femoral paddle axis. The femoral paddle axis mayseparate the femoral paddle into a femoral medial side and a femorallateral side. The tibial paddle may extend along a central tibial paddleaxis. The tibial paddle axis may separate the tibial paddle into atibial medial side and a tibial lateral side. The femoral paddle axisand the tibial paddle axis may be parallel to each other and lie on afirst plane. A femoral paddle shaft may couple the femoral paddle to thehousing and a tibial paddle shaft may couple the tibial paddle to thehousing. The femoral paddle shaft may extend along a femoral paddleshaft axis and the tibial paddle shaft may extend along a tibial paddleshaft axis. The femoral paddle shaft axis and the tibial paddle shaftaxis may be parallel to each other and lie on a second plane. The firstplane may be offset to the second plane.

Continuing in accordance with this aspect, the distractor may include adistraction screw to move the tibial paddle and/or the femoral paddlealong a distraction axis transverse to the femoral paddle shaft axis andthe tibial paddle shaft axis. The tibial paddle may include an aperturefor receiving an anti-rotation shaft extending from the housing toprevent rotation of tibial paddle about the tibial paddle shaft axis.The housing may include an adjuster to translate the femoral paddlealong an adjuster axis transverse to the distraction axis. The femoralpaddle shaft may be rotatable about the femoral paddle shaft axis torotate the femoral paddle with respect to the distraction axis. A medialload center of a medial condyle in contact with the femoral medial sidemay lie on a medial load center axis. A lateral load center of a latercondyle in contact with the femoral lateral side may lie on a lateralload center axis. A medial offset distance measured between the medialload center axis and the femoral paddle shaft axis along the femoralpaddle may be less than a lateral offset distance measured between thelateral load center axis and the femoral paddle shaft axis along thefemoral paddle. The lateral offset distance may allow the femoral paddleand tibial paddle to be placed between a femur and a tibia inposterior-anterior direction without everting a patella.

In a further aspect of the present disclosure, an apparatus forperforming an orthopedic procedure on a knee is provided. An apparatusaccording to this aspect may include a femoral paddle, a tibial paddleand a housing. The femoral paddle may define a thickness. The femoralpaddle may have a proximal side and an opposite distal side. Theproximal side may include at least one proximal femoral recess. Thedistal side may include a distal femoral recess. The tibial paddle mayinclude a tibial proximal side and an opposite tibial distal side. Thehousing may be coupled to the tibial paddle and the femoral paddle. Thehousing may include a distractor to vary the distance between the tibialpaddle and the femoral paddle. The tibial paddle may be disposed withinthe distal femoral recess in a closed position. A combined thickness ofthe femoral paddle and the tibial paddle in the closed position may beequal to the thickness.

Continuing in accordance with this aspect, a load sensor may be disposedin the femoral recess to indicate a load on the femoral paddle.

In a further aspect of the present disclosure, a method of performing anorthopedic procedure on a knee is provided. A method according to thisaspect may include the steps of resecting a proximal tibia, placing afemoral paddle and a tibial paddle of a tensor in a closed positionwithout everting a patella, distracting the knee joint using a housingcoupled to the tibial paddle and the femoral paddle, and measuring kneeloads using a load sensor disposed in a femoral recess of the femoralpaddle to indicate a load on the femoral paddle. The femoral paddle maycontact an unresected distal femur. The tibial paddle may contact theresected proximal tibia in the closed position. The femoral paddle maydefine a thickness. The femoral paddle may have a proximal side and anopposite distal side. The proximal side may include the at least oneproximal femoral recess. The distal side may include a distal femoralrecess. The tibial paddle may include a tibial proximal side and anopposite tibial distal side. The housing may include a distractor tovary the distance between the tibial paddle and the femoral paddle. Thetibial paddle may be disposed within the distal femoral recess such thata combined thickness of the femoral paddle, the tibial paddle and theload sensor in the closed position may be substantially the same as thethickness.

Continuing in accordance with this aspect, the method may furtherinclude the step of taking the knee joint through flexion and extensionto measure knee gap and knee tension while the patella remains everted.

In a further aspect of the present invention, a method of performing anorthopedic procedure on a knee is provided. A method according to thisaspect may include the steps of placing a femoral paddle and a tibialpaddle of a knee balancer in a closed position, distracting the kneejoint using a housing coupled to the tibial paddle and the femoralpaddle, and measuring knee loads using a load sensor disposed in afemoral recess to indicate a load on the femoral paddle. The femoralpaddle may contacts a distal femur and the tibial paddle may contacts aproximal tibia in the closed position. The femoral paddle may define athickness. The femoral paddle may have a proximal side and an oppositedistal side. The proximal side may include the at least one proximalfemoral recess. The distal side may include a distal femoral recess. Thetibial paddle may include a tibial proximal side and an opposite tibialdistal side. The housing may including a distractor to vary the distancebetween the tibial paddle and the femoral paddle. The tibial paddle maybe disposed within the distal femoral recess such that a combinedthickness of the femoral paddle, the tibial paddle and the load sensorin the closed position may be substantially the same as the thickness.

In a further aspect of the present invention, a method of trialing aknee joint for determining an appropriate size for a tibial insert isprovided. A method according to this aspect may include the steps ofinserting first and second members into a space between a tibia and afemur, engaging a first concave surface of the first member with a firstcondylar portion of a femoral component or femur, operating anadjustment mechanism to move the first and second members apart a firstknown distance corresponding to a first size tibial insert, andarticulating the first condylar portion of the femoral component orfemur with the first condylar portion of a tibial component or tibiathrough a range of flexion and extension motion to assess the knee jointat the first known distance. The first and second members may beconnected to an adjustment mechanism. The first member may have thefirst condylar portion defining a first concave surface.

Continuing in accordance with this aspect, the second member may includea first plate and a first arm. The first plate may include the firstcondylar portion of the first member. The first arm may be connected tothe adjustment mechanism. The method may further include the step ofconnecting the first arm to the first plate. The step of connecting thefirst arm to the first plate may include sliding the first arm in alateral-medial direction into a recess defined in a bottom side of thefirst plate. The step of connecting the first arm to the first plate mayinclude sliding the first arm in an anteroposterior direction into arecess defined in a bottom side of the first plate.

Continuing in accordance with this aspect, the method may include thestep of operating the adjustment mechanism to move the first and secondmembers apart a second known distance corresponding to a second sizetibial insert, articulating the first condylar portions of the firstmember and femoral component to assess the knee joint at the secondknown distance.

Continuing in accordance with this aspect, the operating step may beperformed by rotating a rack engaged to a pinion.

Continuing in accordance with this aspect, the engaging step may includeengaging a second concave surface of a second condylar portion of thefirst member with a second condylar portion of a femoral component.

Continuing in accordance with this aspect, the method may furtherinclude engaging a bone contact surface of the second member with aresected proximal surface of the tibia. The second member may include asecond plate and a second arm. The second plate may include the bonecontact surface. The second arm may be connected to the adjustmentmechanism. The method may further include connecting the second arm tothe second plate.

In a further aspect of the present disclosure, a tibial trial system isprovided. A tibial trial system according to this aspect may include anupper plate with an upper articular surface, an upper arm, a lower armand an adjustment mechanism connected to the upper and lower arms. Theupper articular surface may have condylar portions each defining aconcave surface configured to articulate with a corresponding condylarportion of a femoral component. The adjustment mechanism may beconfigured to move the upper and lower arms relative to each other. Theupper arm may be separately formed from the upper plate and may beconnectable to the upper plate.

Continuing in accordance with this aspect, the adjustment mechanism maybe connected to a respective outer end of each of the upper arm andlower arm and configured to adjust a spacing between the upper and lowerarms in a proximal-distal direction when the upper and lower arms aredisposed between a proximal tibia and distal femur.

Continuing in accordance with this aspect, the adjustment mechanism maybe a rack and pinion mechanism. The adjustment mechanism may include ashaft extending in a transverse direction relative to a direction of thespacing and may include a series of teeth extending along the shaft. Agear may be disposed within a housing and operatively engaged with theseries of teeth. The shaft may be connected to the upper arm. Thehousing may be connected to the lower arm.

Continuing in accordance with this aspect, the upper plate may have alower side opposite the articular surface. The lower side may define arecess configured to receive the upper arm. The recess may extend in alateral-medial direction such that the upper arm may be slidinglyreceived by the recess from a lateral or medial side of the upper plate.The recess may extend in an anteroposterior direction such that theupper arm may be slidingly received by the recess from an anterior sideof the upper plate. The recess may define a pair of opposing grooveswhich may be configured to receive opposing side edges of the upper arm.

Continuing in accordance with this aspect, the system may include alower plate having a bone contact surface configured to engage aproximal resected surface of a tibia. The lower arm may be configured toconnect to the lower plate.

Continuing in accordance with this aspect, the lower arm may have aplanar bone contact surface configured to engage a proximal resectedsurface of a tibia.

In a further aspect of the present disclosure, an adjustable tibialtrial insert assembly is provided. An adjustable tibial trial insertassembly according to this aspect may include an upper plate, an upperarm, a lower arm and an adjustment mechanism. The upper plate mayinclude an upper articular surface configured to allow a femoralcomponent to articulate through a range of motion in flexion andextension therewith. The upper arm may be releasably connected to theupper plate and extend in a transverse direction relative to an axis ofthe tibia when the upper arm is disposed between a proximal tibia and adistal femur. The lower arm may extend in the transverse direction. Theadjustment mechanism may be connected to each of the upper arm and lowerarm and configured to adjust a spacing between the upper plate and thelower plate.

Continuing in accordance with this aspect, the lower arm may have aplanar surface configured to contact a proximal resected surface of atibia.

Continuing in accordance with this aspect, the trial insert may furtherinclude a lower plate that may have a lower surface configured to engagea proximal resected surface of a tibia. The upper arm may be releasablyconnected to the lower plate.

Continuing with this aspect, the articular surface may include a pair ofconcave surfaces for engaging respective distal condyles of a femoralcomponent. The concave surfaces may each extend in an anteroposteriordirection. The upper arm and the lower arm may extend in alateral-medial direction.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the subject matter of the presentdisclosure and the various advantages thereof can be realized byreference to the following detailed description, in which reference ismade to the following accompanying drawings:

FIG. 1 is a perspective side view of a tensor of the present disclosure;

FIG. 2 is a perspective top view of a femoral paddle of the tensor ofFIG. 1;

FIG. 3 is a perspective bottom view of the femoral paddle of FIG. 2;

FIG. 4 is a perspective side view of a tibial paddle of the tensor ofFIG. 1;

FIG. 5 is a perspective side view of a housing of the tensor of FIG. 1;

FIG. 6 is a side cross-sectional view of an adjuster along line A-A ofthe housing of FIG. 5;

FIG. 7 is a partial side cross-sectional view of the tensor of FIG. 1along line B-B;

FIG. 8 is a schematic top view of the tensor of FIG. 1 placed in a kneejoint;

FIG. 9 is a perspective view of a load sensor of the tensor of FIG. 1;

FIG. 10 is a side view of the tensor of FIG. 1 placed in a knee joint;

FIGS. 11A-C are top cross-sectional views of the femoral paddle and thetibial paddle of the tensor of FIG. 1;

FIG. 12 is a side perspective view of a balancer according to anotherembodiment of the present disclosure;

FIG. 13 is a perspective view of a flat tibial trial used with thebalancer of FIG. 12;

FIG. 14 is a perspective view of a set of articular tibial trials usedwith the balancer of FIG. 12;

FIG. 15 is a schematic view of an articular tibial trial of FIG. 14 andthe balancer of FIG. 12;

FIG. 16 is a schematic view of the articular tibial trial of FIG. 14placed on the balancer of FIG. 12, and

FIG. 17 is a front perspective view of a balancer according to anotherembodiment of the present disclosure.

DETAILED DESCRIPTION

In describing preferred embodiments of the disclosure, reference will bemade to directional nomenclature used in describing the human body. Itis noted that this nomenclature is used only for convenience and that itis not intended to be limiting with respect to the scope of theinvention.

As used herein, when referring to bones or other parts of the body, theterm “anterior” means toward the front part or the face, and the term“posterior” means toward the back of the body. The term “medial” meanstoward the midline of the body, and the term “lateral” means away fromthe midline of the body. The term “superior” means closer to the heart,and the term “inferior” means more distant from the heart.

Reference will now be made in detail to the various embodiments of thepresent disclosure illustrated in the accompanying drawings. Whereverpossible, the same or like reference numbers will be used throughout thedrawings to refer to the same or like features. It should be noted thatthe drawings are in simplified form and are not drawn to precise scale.Additionally, the term “a,” as used in the specification, means “atleast one.” The terminology includes the words above specificallymentioned, derivatives thereof, and words of similar import. Although atleast two variations are described herein, other variations may includeaspects described herein combined in any suitable manner havingcombinations of all or some of the aspects described. As used herein,the terms “distractor” and “tensor” will be used interchangeably and assuch, unless otherwise stated, the explicit use of either term isinclusive of the other term. Similarly, the terms “aperture,” “hole,”and “recess” will be used interchangeably and as such, unless otherwisestated, the explicit use of either term is inclusive of the other term.

Referring now to FIG. 1, there is shown a perspective view of a tensor10 according to an embodiment of the present disclosure. Tensor 10includes a femoral paddle 100 and a tibial paddle 200 attached to ahousing 300. Tensor 10 can be used to perform various functions during aTKA procedure to achieve the desired knee joint biomechanics as morefully described below. While tensor 10 described herein is configured tobe placed in a subject's left knee joint in an anterior-to-posteriordirection, it should be understood that the features of tensor 10 aresimilar for a tensor configured to be placed in a subject's right kneein an anterior-to-posterior direction. It is also envisioned that tensor10 can be placed in subject's knee joint from a posterior-to-anterior,medial-to-lateral, or lateral-to-medial direction. In such embodiments,housing 300 connects to femoral and tibial paddles 100, 200 at differentlocations depending on the approach. For example, where the approach islateral-to-medial, housing 300 connects to a lateral side of paddles100, 200.

FIG. 2 shows a top view of femoral paddle 100 of tensor 10. Femoralpaddle 100 includes a femoral plate 102 having a thickness T1. Femoralplate 102 extends along a femoral plate axis L4, which divides femoralplate 102 into a femoral lateral side 107 and a femoral medial side 105.A recess 110 runs along the peripheral edge of femoral plate 102 andserves as a receptacle to receive a load sensor. A shaft 106 extendingfrom femoral plate 102 along a shaft axis L1 couples femoral paddle 100to housing 300. Shaft 106 can be rotated either manually or with asuitable tool around shaft axis L1. A groove or notch 108 at the distalof shaft 106 allows for attachment of the tool that can be used torotate femoral plate 102. As best shown in FIG. 2, shaft axis L1 isoffset from femoral plate axis L4. Femoral paddle 100 includes a slot104 to receive a corresponding post from housing 300 as explained below.

Referring now to FIG. 3, there is shown a bottom view of femoral paddle100. Tiered pockets 112, 114, 116, 118 are located across femorallateral side 107 and femoral medial side 105. The tiered pockets aresized and positioned to receive corresponding tiered ribs from tibialpaddle 200 as more fully described below. In addition, tiered pockets112, 114, 116, and 118 are located at different depths within paddle100.

FIG. 4 shows a top view of tibial paddle 200. Tibial paddle includes atibial plate 202 extending along a tibial plate axis L5. A tibial shaft207 extends from tibial plate 202 along a shaft axis L7. Tibial shaftaxis L7 and shaft axis L1 lie on a first plane parallel to a secondplane containing the femoral plate axis L4 and the tibial plate axis L5(not shown). The tibial shaft includes structural reinforcements such asstructure 209 to structurally strengthen tensor 10 and maximize loadcapacity of the tensor. A bore 206 located on tibial shaft 207 extendstransverse to the tibial shaft and is configured to receive acorresponding shaft from housing 200. A distraction mechanism—e.g., ascrew 210 attached to bore 206 in this embodiment, allows fortranslation of femoral paddle 100 in reference to tibial paddle 200. Ananti-rotation post 208 configured to be received in a correspondingrecess of housing 300 prevents rotation of tibial paddle 300. Variousholes 204 located on tibial paddle 200 serve as drill guides oralignment references during a balancing procedure. A set of tiered ribs212, 214, 216 and 218 are provided on a proximal side of tibial plate202 as best shown in FIG. 4. Such tiered ribs 212, 214, 216, and 218extend from the proximal side at differing heights which correspond tothe depths of the respective tiered pockets 112, 114, 116, and 118. Inthis regard, each tiered rib is configured to lie within a correspondingtiered pocket of femoral plate 102. When tibial plate 202 and femoralplate 102 are brought together by the distraction mechanism, the tieredribs 212, 214, 216, 218 of tibial plate 202 are designed to bepositioned within the corresponding pockets 112, 114, 116, 118 offemoral plate 102 such that tibial plate 202 lies completely withinfemoral plate 102.

FIGS. 11A-11C show cross-sectional views of the tiered rib and pocketinterface of tensor 10 in a collapsed state when the tibial plate 202lies entirely within femoral plate 102. As shown in FIG. 11A, tiered rib212 of tibial plate 202 is received within pocket 112 of femoral plate102. Similarly, tiered rib 216 is received in pocket 116 (FIG. 11B) andtiered rib 218 is received in pocket 118 (FIG. 11C) when tensor 10 is inthe collapsed state. The tiered rib and pocket interface allow forincreased load bearing capacity of tensor 10 while simultaneouslyensuring a low paddle profile to allow the tensor to be placed in thenarrow gap between a femur and a tibia. For example, the combinedthickness T1 of the femoral paddle, sensor array and the tibial paddleis constructed to be 6.1 mm or less. Despite this low profile, thetiered pockets, tiered ribs and reinforcing gussets enable the tensor tobe robust enough to withstand at least 200 pounds per condyle or a totalof at least 400 pounds. While a femoral plate with tiered pockets and atibial plate with tiered ribs is shown in the present embodiment, inanother embodiment the femoral plate can have tiered ribs and the tibialplate can have corresponding tiered recesses.

Referring now to FIG. 5, a perspective view of housing 300 is shown.Housing 300 includes a shaft 306 designed to be placed in bore 206 tocouple the housing with tibial paddle 200. A bore 304 extendingtransverse to shaft 306 is configured to receive shaft 106 of femoralpaddle 100 to couple the housing with the femoral paddle. A bore 308 isconfigured to receive anti-rotation post 208 from tibial paddle 200 inorder to prevent rotation of tibial paddle 200 with reference to housing300. An adjuster 302 for varying varus-valgus of the joint is located onhousing 300 allowing for linear translation of femoral plate 102 as morefully explained below.

FIG. 6 shows a cross-sectional view of adjuster 302 along line A-A ofFIG. 5. Adjuster 302 includes a screw 314 located between end washers310 and an end cap 312. The adjuster has a post 316 extending from screw314 that can be placed in slot 104 of femoral paddle 100. Screwthreading 318 of screw 314 allow the adjuster to translate the femoralplate 102 via post 316. This translation allows for varus-valgusadjustment of the knee described below. End washers 310 and end cap 312restrict movement of the femoral paddle confining translation of thefemoral plate to rotation of screw 314.

FIG. 7 shows a cross-sectional view along line B-B of FIG. 1 depictingthe various adjustment mechanisms of tensor 10. Shaft 106 of femoralpaddle 100 can be rotated about shaft axis L1 to move femoral paddle 102to various positions to adjust varus/valgus rotation of the knee for adesired joint orientation. For example, shaft 106 can be rotatedcounterclockwise to locate femoral plate to a second position 102′ toprovide a valgus rotation angle 322. Similarly, shaft 106 can be rotatedin an opposite clockwise direction to locate femoral plate to a thirdposition 102″ to provide a varus rotation angle 324 as best shown inFIG. 7. Adjuster 302 allows for linear translation of femoral plate 102along a translation axis 320 transverse to shaft axis L1. As indicatedby the position of post 316, adjuster 302 can move the femoral platefrom the first location to a second location 316′ or a third location316″ in the opposite direction. The linear translation along translationaxis 320 allows a surgeon to control internal and external rotation ofthe joint. A rotation indicator 326 on adjuster 302 indicates theexternal or internal rotation of femoral plate 102 as best shown in FIG.5

Referring now to FIG. 8, there is shown a schematic top view of tensor10 placed over a resected tibia 14 with patellar tendon 12 being movedlaterally away to accommodate the femoral and tibial paddles of tensor10. As shown here, the shaft lengths (femoral shaft 106 and tibial shaft207) and the plate offsets from shaft axis L1 (femoral plate 102 andtibial plate 202), allow tensor 10 to be located in the knee jointwithout everting the patella. Femoral load centers during extension andflexion of the knee joint are also shown in FIG. 8. A load center 122 onfemoral medial side 105 of femoral plate 102 is located on medial loadaxis L2 representing a femoral medial condyle load during extension andflexion of the knee joint. Load center 122 is offset from shaft axis L1by a distance D1. Femoral lateral side 107 includes a first load center124 representing the lateral condyle load in extension of the knee, anda second load center 126 representing the lateral condyle load inflexion. Load centers 124 and 126 lie on lateral load axis L3 as shownin FIG. 8, which is offset from shaft axis L1 by a distance D2. Asdistance D2 is greater than D1, tensor 10 will be subject torsionalloads during balancing. However, the plate offsets allow tensor 10 to beplaced in anterior-to-posterior direction in a subjects left knee jointwithout requiring the eversion of the subject's patella. As best shownin FIG. 8, housing 300 and shaft 106, 207 can lie medial to patellartendon 12, while the laterally extending femoral lateral side 107 offemoral plate 102 can contact the lateral condyle of the subject. Tensor10 can be maintained in this position while the knee is being takenthrough its range of motion from flexion to extension during balancing.

FIG. 9 shows a perspective view of a load sensor 134 that can be placedin recess 110 of femoral plate 102. Load cells 132 and sensor loadplates 134 are sized and shaped to fit within femoral plate 102 andcontact load centers 122, 124 and 126 during flexion and extension toindicate femoral load values. A sensor housing 130 can include aprocessor, a power source and other components necessary for loadreading and transmission. The sensor housing is located on the femoralshaft away from femoral plate 102 to ensure that only load cells 132 andsensor load plates 128 of load sensor 134 are located in femoral plate102 to minimize the thickness of the femoral plate. Tensor 10 allows forconvenient placement and removal of load sensor 134. While tensor 10described herein includes a load sensor, it should be understood thattensor 10 can be used without the load sensor.

Referring now to FIG. 10, there is shown a side view of tensor 10 placedin a subject's knee joint. Tibial plate 202 lies entirely with femoralplate 102 when the femoral and tibial paddles are brought together asshown in FIG. 10. When the paddles are in this collapsed state, thecombined thickness of the femoral plate including load sensor 134 andtibial plate is equal to thickness T1 of femoral plate. While a loadsensor may lie completely within recess 110 of femoral plate 102 suchthat the load sensor does not extend past the thickness of femoralplate, in another embodiment the thickness of load sensor 134 mayslightly extend past the femoral plate thickness.

Another aspect of the present disclosure is a method for performing aTKA with a tensor such as tensor 10. After resecting the proximal tibia14, tensor 10 with its femoral paddle and tibial paddle fullyretracted—i.e., in the collapsed state, is inserted into the knee jointas shown in FIG. 10. The low profile of tensor 10 in the collapsed stateallows the tensor to be inserted in an anterior-to-posterior directionwithout resecting a proximal femur 16. Of course, the proximal femur canbe resected prior to insertion if desired. Furthermore, as more fullydescribed above, the shaft lengths (femoral shaft 106 and tibial shaft207) and the plate offsets (femoral plate 102 and tibial plate 202) fromshaft axis L1, allow tensor 10 to be located in the knee joint withouteverting the patella. Once the tensor 10 is firmly located in the kneejoint, the tensor can be used to perform various functions to measureand achieve the desired knee joint biomechanics. Tensor 10 can bemaintained in this position while the knee is being taken through itsrange of motion from flexion to extension during balancing. For example,the femoral paddle and tibial paddle can be separated using screw 210 toadjust the gap between tibia 14 and femur 16, adjuster 302 can be usedto translate femoral plate 102 to adjust varus/valgus andinternal/external rotation of the knee joint, and shaft 106 can berotate to adjust varus/valgus rotation of knee joint. Furthermore,real-time load values of the lateral and medial condyles of femur 16 aremeasured and communicated to an operator during flexion and extension ofthe knee joint.

Referring now to FIG. 12, there is shown a balancer 400 according toanother embodiment of the present disclosure. Balancer 400 is anadjustable tibial spacer and balancer that allows for trialing of atibial spacer during a TKA procedure. Balancer 400 includes a femoralplate 402 and a tibial plate 404 coupled to a housing 405. Housing 405includes a rack and pinion distraction mechanism which is used to varythe distance between femoral plate 402 and tibial plate 404. A rotationindicator 410 provided on housing 405 allows for varus/valgus rotationadjustments of femoral plate 402. A lock pin 412 allows an operator tolock the varus/valgus rotation of femoral plate. The lock pin can bereleased to rotate the femoral plate to achieve the desired varus/valgusalignment. Once the desired varus/valgus alignment is achieved the lockpin can be activated to secure femoral plate alignment. Thicknessindicators 416 indicate the tibial spacer size—i.e., distraction gapbetween the femoral and tibial plates, and can be locked into place oncethe desired tibial spacer size is achieved.

FIGS. 13 and 14 show various attachments that can be readily attached toa distal end 406 of femoral plate 402. A flat tibial trial 500 is shownin FIG. 13. Flat tibial trial 500 includes an opening 502 shaped andsized to be removably connected to distal end of femoral plate 402.Opening 502 can have various features such as grooves, notches, tabs,etc. that can readily attached to mating features present on distal end406 of femoral plate 402. A flat surface 504 of flat tibial trial 500contacts a proximal femur or a femoral component when the flat tibialtrial is placed in a knee joint. While opening 502 shown here extends inan anterior-to-posterior direction, another embodiment can have anopening extending in a medial-to-lateral direction. A flat tibial trialhaving an opening 502 extending in a medial-to-lateral direction can beslidably engaged with balancer 400 and placed in a knee joint in amedial-to-lateral direction to prevent everting of the patella during aTKA. Flat tibial trial 500 can be attached to balancer 400 and insertedto a knee joint to determine the proper tibial spacer thickness forbalanced extension and flexion gaps. Thickness indicator 416 is used tolock in the desired thickness.

A set of articular tibial trials 602, 604, 606, 608 are shown in FIG.14. The articular tibial trials are similar to flat tibial trial 500 andinclude an opening 610 for attachment to femoral plate 402. However,articular tibial trials include an articular surface with concavesurfaces to contact medial and lateral condyles of a femur or femoralimplant. The articular tibial trials allow the knee joint to be takenthrough a range of motion from flexion to extension by providing anarticular surface for the femoral condyles to articulate during therange of motion. The articular tibial trials are provided in varioussizes that can be readily attached and detached from femoral plate 402.The tibial trial sizes can be limited to a small number, as thedistraction mechanism of balancer 400 can be used to adjust to trial fortibial spacers that are larger or smaller than the available tibialtrials. As described above, openings 610 of articular tibial trials canextend in a medial-to-lateral direction to allow placement of thebalancer 400 in a knee joint in a medial-to-lateral or lateral-to-medialdirection.

Another aspect of the present disclosure is a method of trialing atibial spacer with a balancer such as balancer 400. Flat tibial trial500 can be readily attached to femoral plate 402 by sliding opening 502of the flat tibial trial into distal end 406. Depending on theorientation of opening 502—i.e., anterior-to-posterior ormedial-to-lateral, the balancer with the attached flat tibial trial isinserted into the knee joint in the same direction. For example, if theopening 502 extends in a lateral-to-medial direction, balancer 400 canbe inserted in lateral-to-medial direction into the knee joint with theattached flat tibial trial. The femoral and tibial plates can bedistracted using distraction mechanism 408 if necessary to determine thedesired knee gap.

Once these desired gap is achieved, the flat tibial trial can be removedfrom balancer and an appropriate articular tibial trial can be attachedto balancer 400. As shown in FIGS. 15, and 16 articular tibial trial 606is slidably connected to femoral plate 402 of balancer 400. The kneejoint can now be taken through a range of motion from flexion toextension to determine the desired joint biomechanics and the tibialspacer size. As attachment tibial trials can be easily attached andremoved from balancer 400, balancer 400 can be removed from theattachment tibial trials once they are placed in the knee joint tofacilitate convenient knee flexion and extension.

FIG. 17 shows a balancer 700 according to another embodiment of thepresent disclosure. Balancer 700 is a fully adjustable tibial spacer andbalancer that allows for trialing of a tibial spacer during a TKAprocedure. Balancer 700 is similar to balancer 400 but is fullyadjustable requiring no tibial trials or trial inserts for trialing of atibial spacer. Balancer 700 includes a first post 706 and a second post708 that can be adjusted to vary the distance between them as indicatedby a distance 712 in FIG. 17. Adjusting the distance between the firstand second posts allows for adjusting the spacing between medial andlateral femoral plates 702 and medial and lateral tibial plates 704 by adistance 714. An operator can adjust the size of the tibial insert byvarying distance 712, which will in turn change the distance betweenfemoral plates 702 and tibial plates 704 via a link 710. Thus, femoraland tibial plate sizes can be increased or decreased by manipulatingfirst post 706 and second post 708 of balancer 700. While distance 714between femoral plates 702 and tibial plates 704 are simultaneouslyvaried by adjusting distance 712 in this embodiment, in anotherembodiment distance between the femoral plates and the tibial plates canbe individually controlled and adjusted.

A distance 716 between femoral plates 702 and tibial plates 704 ofbalancer 700 is also adjustable. Depending on the required thickness ofthe tibial insert, an operator can increase or decrease distance 716 toincrease or decrease the thickness of femoral and tibial plates of 700.Thus, balancer 700 provides a fully adjustable tibial inserter allowingan operator to increase the size and thickness of a tibial insertwithout requiring the need for any tibial inserts. While a typicalsurgical kit to perform a TKA may include as many as 576 differenttibial inserts with different sizes, thickness and procedure-specificconfigurations, balancer 700 can be utilized without any tibial insertsas balancer 700 is fully adjustable to assume the shape, size andconfiguration of any required tibial insert.

While a TKA procedure is generally described in these embodiments, theapparatus and methods of the present disclosure can be used for variousother knee and hip procedures or any part of these procedures. Thevarious components of tensor 10 and balancer 400 can be modular. Forexample, the housing of tensor 10 can be configured to couple withfemoral and tibial paddles of various sizes. Tensors and balancersdisclosed herein can be made wholly, or in part, by polymers such asPEEK, carbon fiber reinforced PEEK, PAEK, UHMWPE, metals, ceramics,combinations of the foregoing, or other suitable materials that arebiocompatible and possess sufficient strength and rigidity. Near netshape casting, subtractive manufacturing techniques, and additivemanufacturing techniques such as 3D printing may be used to fabricatethe tensor and balancers of the present disclosure.

Furthermore, although the invention disclosed herein has been describedwith reference to particular features, it is to be understood that thesefeatures are merely illustrative of the principles and applications ofthe present invention. It is therefore to be understood that numerousmodifications, including changes in the sizes of the various featuresdescribed herein, may be made to the illustrative embodiments and thatother arrangements may be devised without departing from the spirit andscope of the present invention. In this regard, the present inventionencompasses numerous additional features in addition to those specificfeatures set forth in the claims below. Moreover, the foregoingdisclosure should be taken by way of illustration rather than by way oflimitation as the present invention is defined in the examples of thenumbered paragraphs, which describe features in accordance with variousembodiments of the invention, set forth in the claims below.

1. An apparatus for performing an orthopedic procedure on a knee, theapparatus comprising: a femoral paddle defining a thickness, the femoralpaddle having a proximal side and an opposite distal side, the proximalside including at least one proximal femoral recess, the distal sideincluding a distal femoral recess; a tibial paddle including a tibialproximal side and an opposite tibial distal side; a load sensor disposedin the femoral recess to indicate a load on the femoral paddle; and ahousing coupled to the tibial paddle and the femoral paddle, the housingincluding a distractor to vary the distance between the tibial paddleand the femoral paddle, wherein in a closed position the tibial paddleis disposed within the distal femoral recess such that a combinedthickness of the femoral paddle, the tibial paddle and the load sensorin the closed position is substantially the same as the thickness. 2.The apparatus of claim 1, wherein the femoral paddle includes aplurality of tiered recesses within the distal femoral recess and thetibial paddle includes a plurality of tiered ribs on the tibial proximalside such that each of the plurality of tiered ribs is disposed within acorresponding tiered recess in the closed position.
 3. The apparatus ofclaim 2, wherein at least one of the tiered ribs contact a distalsurface of the corresponding tiered recess in the closed position. 4.The apparatus of claim 1, wherein the femoral paddle extends along acentral femoral paddle axis, the femoral paddle axis separating thefemoral paddle into a femoral medial side and a femoral lateral side,and the tibial paddle extends along a central tibial paddle axis, thetibial paddle axis separating the tibial paddle into a tibial medialside and a tibial lateral side.
 5. The apparatus of claim 4, wherein thefemoral paddle axis and the tibial paddle axis are parallel to eachother and lie on a first plane.
 6. The apparatus of claim 5, wherein afemoral paddle shaft couples the femoral paddle to the housing and atibial paddle shaft couples the tibial paddle to the housing.
 7. Theapparatus of claim 6, wherein the femoral paddle shaft extends along afemoral paddle shaft axis and the tibial paddle shaft extends along atibial paddle shaft axis.
 8. The apparatus of claim 7, wherein thefemoral paddle shaft axis and the tibial paddle shaft axis are parallelto each other and lie on a second plane.
 9. The apparatus of claim 8,wherein the first plane is offset to the second plane.
 10. The apparatusof claim 1, wherein the distractor includes a distraction screw to movethe tibial paddle and/or the femoral paddle along a distraction axistransverse to the femoral paddle shaft axis and the tibial paddle shaftaxis.
 11. The apparatus of claim 10, wherein the tibial paddle includesan aperture for receiving an anti-rotation shaft extending from thehousing to prevent rotation of tibial paddle about the tibial paddleshaft axis.
 12. The apparatus of claim 11, wherein the housing includesan adjuster to translate the femoral paddle along an adjuster axistransverse to the distraction axis.
 13. The apparatus of claim 12,wherein the femoral paddle shaft is rotatable about the femoral paddleshaft axis to rotate the femoral paddle with respect to the distractionaxis.
 14. The apparatus of claim 9, wherein a medial load center of amedial condyle in contact with the femoral medial side lies on a medialload center axis and a lateral load center of a later condyle in contactwith the femoral lateral side lies on a lateral load center axis. 15.The apparatus of claim 14, wherein a medial offset distance measuredbetween the medial load center axis and the femoral paddle shaft axisalong the femoral paddle is less than a lateral offset distance measuredbetween the lateral load center axis and the femoral paddle shaft axisalong the femoral paddle.
 16. The apparatus of claim 15, wherein thelateral offset distance allows the femoral paddle and tibial paddle tobe placed between a femur and a tibia in posterior-anterior directionwithout everting a patella.
 17. An apparatus for performing anorthopedic procedure on a knee, the apparatus comprising: a femoralpaddle defining a thickness, the femoral paddle having a proximal sideand an opposite distal side, the proximal side including at least oneproximal femoral recess, the distal side including a distal femoralrecess; a tibial paddle including a tibial proximal side and an oppositetibial distal side; and a housing coupled to the tibial paddle and thefemoral paddle, the housing including a distractor to vary the distancebetween the tibial paddle and the femoral paddle, wherein in a closedposition the tibial paddle is disposed within the distal femoral recesssuch that a combined thickness of the femoral paddle and the tibialpaddle in the closed position is equal to the thickness.
 18. Theapparatus of claim 17, further including a load sensor disposed in thefemoral recess to indicate a load on the femoral paddle.
 19. A method ofperforming an orthopedic procedure on a knee, the method comprising thesteps of: resecting a proximal tibia; placing a femoral paddle and atibial paddle of a knee balancer in a closed position without everting apatella, the femoral paddle contacting an unresected distal femur andthe tibial paddle contacting the resected proximal tibia in the closedposition, the femoral paddle defining a thickness, the femoral paddlehaving a proximal side and an opposite distal side, the proximal sideincluding at least one proximal femoral recess, the distal sideincluding a distal femoral recess, the tibial paddle including a tibialproximal side and an opposite tibial distal side; distracting the kneejoint using a housing coupled to the tibial paddle and the femoralpaddle, the housing including a distractor to vary the distance betweenthe tibial paddle and the femoral paddle; and measuring knee loads usinga load sensor disposed in the femoral recess to indicate a load on thefemoral paddle, wherein the tibial paddle is disposed within the distalfemoral recess such that a combined thickness of the femoral paddle, thetibial paddle and the load sensor in the closed position issubstantially the same as the thickness.
 20. The method of claim 19,further including the step of taking the knee joint through flexion andextension to measure knee gap and knee tension while the patella remainseverted.